Foveon improves its X3 Pro 10M image sensorBy
Mike Tomkins(Sunday, October 26, 2003 - 19:00 EST)Foveon Inc., the company behind the X3 Pro 10M image sensor (model number F7X3-B91) used in Sigma's SD9 digital camera, has today announced an updated version of the imager.

The company is referring to the new F7X3-C9110 image sensor as a 10.2 megapixel sensor, since it has 10.2 million photosensitive cells (or photosites) which are effective in creating the final image - but as with the other X3 sensors (and Fujifilm's SuperCCD SR sensor), this isn't quite the whole story. The Japan Camera Industry Association (JCIA) - of which Foveon's partner Sigma is a member - has defined the meaning of a megapixel, but unfortunately that definition was written over a year before Foveon and Fujifilm's sensors were created. Worse still, the current definition is subject to a good deal of interpretation.

Our reading of the definition suggests that Foveon's original approach - referring to the sensor's luminance resolution appended with "x 3" - was probably closest to the intent of the document. The thing is, that's all it is - our opinion; give the document to somebody else to read and they might arrive at an entirely different opinion. A deep discussion of the topic is beyond this article (and the X3F Info Page has a great discussion of it already). Suffice to say, we'd like to see the manufacturers get together and hammer out a better definition - one that isn't confusing to consumers, and isn't biased towards a particular sensor format. In the meantime, we feel more comfortable referring to Foveon's sensor as a 3.4 megapixel chip which measures full color at every pixel location (or "3.4 megapixel x 3", as is recommended for multi-chip digital still cameras).

That commentary aside, the new chip (which is available to manufacturers immediately) sounds to be quite an improvement based on the information given by Foveon. As well as unspecified improvements to the sensor design and fabrication process, the addition of microlenses to the sensor improves the effective fill factor - recapturing light that would otherwise be falling outside the area of the photosensitive cell. This in turn raises the chip's sensitivity - Foveon comments that it "doubles the sensitivity and maximum exposure times and offers increased dynamic range over its predecessor". Microlenses are used on most digital SLRs, and they do bring potential disadvantages. Two in particular stand out - the potential for abberations such as the purple fringing around extremely bright areas of an image, and vignetting towards the corners of an image caused by light striking the sensor at a high angle of incidence. These are likely to be more of a problem on paper than in real life, simply because the size of the C9110 sensor is much smaller than that of 35mm film - so it will be using the so-called "sweet spot" at the center of 35mm lenses where light is entering the sensor at close to perpendicular.

As might be expected, the first customer for the new chip will be Sigma - who are anouncing an updated version of the SD9 digital camera alongside Foveon's announcement. Specifics on the new F7X3-C9110 image sensor courtesy of Foveon follow:

Foveon X3 Pro 10M CMOS Direct Image Sensor F7X3-C9110

Features

FoveonX3® Technology

Three pixel sensors are layered at each pixel location to achieve superior color fidelity through full-measured color.

Images have improved sharpness and immunity to sampling artifacts (moiré).

Foveon X3 technology directly converts light of all colors into useful signal information at every pixel location—no light absorbing filters are used to block out light.

Variable Pixel Size (VPS) Capability

Several neighboring pixels can be grouped together on-chip to obtain the effect of a larger pixel.

Enables flexible video capture at a variety of resolutions.

Enables higher ISO mode at lower resolutions.

Reduces noise by combining pixels.

Ultra Low Power

Use of the most advanced CMOS process technology allows for ultra low power.

Input voltages to the image sensor are less than 2.5V.

Power consumption is less than 50 mW during readout, less than 10 mW in standby mode,and less than 100 µW in power down mode.

Santa Clara, CA (October 27, 2003) – Foveon Inc., a technology leader in high-quality digital photography, announces the immediate availability of the F7X3-C9110, an enhanced version of the Foveon X3® PRO 10M image sensor. The improved 10.2 megapixel (red + green + blue pixels) image sensor doubles the sensitivity and maximum exposure times and offers increased dynamic range over its predecessor. The new Foveon sensor is used in the Sigma SD10 digital Single-Lens Reflex (SLR) camera. The new Foveon X3® PRO 10M image sensor will allow users to capture outstanding photographs at higher shutter speeds ideal for sports action as well as in low light situations requiring long exposures up to 30 seconds.

The new Foveon image sensor is a result of design and fabrication process improvements that result in higher image quality and superb color fidelity. “These improvements demonstrate the speed at which we are evolving the technology and support our confidence that X3 is the most advanced image sensor technology for capturing color images,” said Federico Faggin, Foveon’s CEO.

The first camera to incorporate the new image sensor is the newly introduced Sigma SD10 digital Single-Lens Reflex (SLR) camera. The camera supports an ISO range from 100 to 800, plus an extended mode option to ISO 1600, and exposure durations of up to 30 seconds.

“The choice of image sensor is becoming a top criterion, when choosing a digital camera, because it is the primary factor that determines the image quality. We believe that with Foveon X3 technology, the Sigma SD10 digital camera offers color resolution and color fidelity comparable to other cameras costing four times the price,” said Faggin.

About Foveon X3 Direct Image Sensors Foveon X3 image sensors are the world’s only direct image sensors, which capture red, green, and blue light at every pixel location, and are the first image sensors that leverage silicon’s inherent color separation property. When silicon is exposed to light, blue light is absorbed near the surface, green light is absorbed in the middle, and red light is absorbed deep within the silicon. Pixel sensors are stacked at the corresponding depths within the silicon so that red, green, and blue light is captured for each pixel location.

Other image sensors on the market such as CCD and CMOS image sensors have only one layer of pixels and use colored filters to capture a single color per location, resulting in color artifacts and image blurring.

About Foveon Since its establishment in 1997, Foveon has focused on the development of image capture technologies and products for digital cameras. Foveon is a privately held company. Investors include: National Semiconductor Inc., Synaptics Inc., New Enterprise Associates, and Franklin Templeton Investments.